Elastic wave resonator and communication device

Abstract

An elastic wave resonator includes: a piezoelectric layer having a groove in a first surface and having piezoelectricity; and a plurality of electrode fingers including a first electrode finger at least partially located in the groove. In a cross-sectional view viewed from the direction in which the plurality of electrode fingers extend, a region of the first electrode finger located within the groove has a wide region and a narrow region having a narrower width than the wide region. The elastic wave resonator excites at least one of a plate wave and a body wave as a main resonance.

Description

Technical Field

[0001] This disclosure relates to an elastic wave resonator as an electronic component utilizing elastic waves, and a communication device comprising the elastic wave resonator. Background Technology

[0002] Patent Document 1 discloses an elastic wave device having a piezoelectric layer and an IDT (interdigital transducer) electrode located on the piezoelectric layer, using an A1 mode plate wave as the elastic wave. The IDT electrode has a plurality of electrode fingers arranged in the propagation direction of the elastic wave. The smaller the spacing between the plurality of electrode fingers, the higher the resonant frequency. The elastic wave device of Patent Document 1 can achieve resonance in the high-frequency region compared to conventional resonators that utilize elastic surface waves as the main resonance, with a spacing equal to that of conventional resonators.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: International Publication No. 2020 / 100949 Summary of the Invention

[0006] An embodiment of the elastic wave resonator disclosed herein includes: a piezoelectric layer having a groove on a first surface and possessing piezoelectricity; and a plurality of electrode fingers, including a first electrode finger at least partially located within the groove. In a cross-sectional view viewed from the extending direction of the plurality of electrode fingers, the region of the first electrode finger located within the groove has a wide region and a narrow region narrower than the wide region. The elastic wave resonator excites at least one of a plate wave and a body wave as the primary resonance.

[0007] One embodiment of the communication device disclosed herein includes: an antenna; an elastic wave filter connected to the antenna; and an integrated circuit (IC) connected to the elastic wave filter. The elastic wave filter includes the aforementioned elastic wave resonator. Attached Figure Description

[0008] Figure 1 This is a schematic cross-sectional view of an elastic wave resonator according to one embodiment of the present disclosure.

[0009] Figure 2 This is a schematic top view of an elastic wave resonator according to one embodiment of the present disclosure.

[0010] Figure 3 In Figure 3 A and Figure 3 B is a schematic cross-sectional view of the electrode fingers of an elastic wave resonator according to one embodiment of the present disclosure.

[0011] Figure 4 This is a graph showing the simulation results of the resonance characteristics of an elastic wave resonator according to one embodiment of the present disclosure.

[0012] Figure 5 In Figure 5 A, Figure 5 B and Figure 5 C is a schematic cross-sectional view of the electrode fingers of an elastic wave resonator according to other embodiments of this disclosure.

[0013] Figure 6 This is a schematic cross-sectional view of an elastic wave resonator according to other embodiments of this disclosure.

[0014] Figure 7 In Figure 7 A and Figure 7 B is a graph representing the simulation results of the frequency characteristics for an embodiment of the present disclosure.

[0015] Figure 8 In Figure 8 A and Figure 8 B is a graph representing the simulation results of the frequency characteristics for an embodiment of the present disclosure.

[0016] Figure 9 In Figure 9 A and Figure 9 B is a graph representing the simulation results of the frequency characteristics for an embodiment of the present disclosure.

[0017] Figure 10 In Figure 10 A and Figure 10 B is a graph representing the simulation results of the frequency characteristics for an embodiment of the present disclosure.

[0018] Figure 11 This is a diagram schematically illustrating a wave demultiplexer as an example of the use of an elastic wave resonator according to one embodiment of this disclosure.

[0019] Figure 12 This is a block diagram showing the structure of the main part of a communication device as an example of the use of an elastic wave resonator according to one embodiment of this disclosure. Detailed Implementation

[0020] Hereinafter, an embodiment of the elastic wave resonator and communication device of the present disclosure will be described with reference to the accompanying drawings. Furthermore, the drawings used in the following description are schematic, and the dimensions and proportions shown in the drawings may not necessarily correspond to those of actual elastic wave resonators and communication devices.

[0021] For ease of explanation, an orthogonal coordinate system consisting of the X-axis, Y-axis, and Z-axis is added to the accompanying drawings. The X-axis is defined as parallel to the propagation direction of the elastic wave used for the main resonance in the propagation of the elastic wave of the piezoelectric layer 2 (described later), the Y-axis is defined as parallel to the extension direction of the electrode finger 412 (described later), and the Z-axis is defined as orthogonal to the upper surface 2a of the piezoelectric layer 2 (described later). Furthermore, the orthogonal coordinate system used in this disclosure is only one example; the X-axis, Y-axis, and Z-axis directions may also be defined as directions different from those used in this disclosure. In this disclosure, for ease of explanation, the Z-axis direction is referred to as the up-down direction, and the terms "upper surface" or "lower surface" are sometimes used.

[0022] The embodiments of the elastic wave resonator disclosed herein are exemplary. Therefore, the structures can be partially substituted in different embodiments. In addition, different embodiments can be partially combined.

[0023] Figure 1 This is a schematic cross-sectional view of an elastic wave resonator 1 according to an embodiment of this disclosure, viewed from the Y-axis direction. Figure 1 As shown, an elastic wave resonator 1 according to one embodiment of the present disclosure has a piezoelectric layer 2, a support substrate 3, an acoustic reflector layer 5, and an IDT electrode 4.

[0024] With the Z-axis as the vertical direction, the piezoelectric layer 2 has an upper surface 2a and a lower surface 2b perpendicular to the Z-axis. The lower surface 2b is located opposite to the upper surface 2a. For example, the upper surface 2a can be referred to as the first surface, and the lower surface 2b as the second surface. The acoustic reflector layer 5 and the support substrate 3, described later, are located on the lower surface 2b side of the piezoelectric layer 2. The IDT electrode 4, described later, is located on the upper surface 2a side of the piezoelectric layer 2.

[0025] The piezoelectric layer 2 contains a piezoelectric material. Examples of piezoelectric materials include single crystals of lithium tantalate (LiTaO3; hereinafter referred to as LT) and single crystals of lithium niobate (LiNbO3; hereinafter referred to as LN).

[0026] The piezoelectric layer 2 is piezoelectric, and when a high-frequency signal is applied to the IDT electrode 4, the elastic wave propagating in the piezoelectric layer 2 is excited. In one embodiment of this disclosure, the excited elastic wave is at least one of a plate wave and a volume wave, serving as the main resonance.

[0027] In one embodiment of this disclosure, the type and propagation mode of the plate wave or bulk wave excited as the main resonance are not particularly limited, and can be set according to the required frequency characteristics. The piezoelectric layer 2 contains a piezoelectric single crystal with Euler angles (…). The parameters (θ, ψ) can also be appropriately designed according to the type and propagation mode of the plate wave or volume wave used as the main resonance. For example, as a type of plate wave, Lamb waves and SH waves can be examples. For example, as a propagation mode of Lamb waves, the A1 mode as an asymmetric mode and the S mode as a symmetric mode can be examples. As a type of volume wave, waves propagating along the plane direction of the piezoelectric layer 2 and waves propagating along the thickness direction of the piezoelectric layer 2 can be examples. Specifically, in one embodiment of this disclosure, the elastic wave excited as the main resonance is the A1 mode of the Lamb wave as a plate wave.

[0028] For example, in the case where the piezoelectric layer 2 is LT, by adjusting the Euler angle of LT ( By setting θ, ψ to (0°±10°, 0° and 55°, 0°±10°) or their crystallographic equivalent angles, the A1 mode of the Lamb wave can be effectively utilized as the main resonance. Referring to Examples 1 and 2 described later, θ, ψ can also be set to (0°±10°, 30°±10°, 0°±10°) or their crystallographic equivalent angles. When the piezoelectric layer 2 is LN, by setting the Euler angles of the LN (θ, ψ)... Setting θ and ψ to (0°±10°, above 0° and below 55°, 0°±10°) or their crystallographic equivalent angles allows for effective utilization of the A1 mode of the Lamb wave as the main resonance. Referring to Examples 3 and 4 described later, θ and ψ can also be set to (0°±10°, 35°±10°, 0°±10°) or their crystallographic equivalent angles.

[0029] A primary resonance, for example, refers to the resonance in which the impedance of a plurality of resonants with different resonant frequencies produced in an elastic wave resonator 1 is minimized (or, from another perspective, the impedance at the resonant frequency is minimized). Furthermore, when a specific elastic wave (e.g., a plate wave) is used as the primary resonance, for example, the aforementioned specific elastic wave is the dominant component of the elastic wave that produces the primary resonance. The dominant component is, for example, the component that accounts for more than 50% or 80% of the energy of the elastic wave at the resonant frequency. When both a plate wave and a volume wave are used as the primary resonance, it is sufficient that the overall energy of both is at the aforementioned value (each can also be less than the aforementioned lower limit).

[0030] When using the wavelength λ described later, the thickness of the piezoelectric layer 2 can be λ or less. By setting the thickness of the piezoelectric layer 2 to λ or less, at least one of the plate wave and the bulk wave can be effectively utilized as the primary resonance. Alternatively, the thickness of the piezoelectric layer 2 can be 0.5λ or less. In this case, at least one of the plate wave and the bulk wave can be utilized more effectively as the primary resonance. Furthermore, it can also be set to 0.4λ or less or 0.3λ or less. The lower limit is not particularly limited, and the piezoelectric layer 2 can be as thin as possible. For example, the thickness of the piezoelectric layer 2 can also be 0.05λ or more, 0.10λ or more, or 0.15λ or more. The above lower and upper limits can be arbitrarily combined.

[0031] The support substrate 3 is located on the lower surface 2b side of the piezoelectric layer 2. The thickness of the support substrate 3 is not particularly limited; for example, the thickness of the support substrate 3 may be thicker than the thickness of the piezoelectric layer 2.

[0032] The material of the support substrate 3 is not particularly limited. For example, the material of the support substrate 3 can be a material with a coefficient of linear expansion smaller than that of the piezoelectric layer 2. By using such a material for the support substrate 3, it is possible to reduce the deformation of the piezoelectric layer 2 caused by temperature changes and the changes in the resonance characteristics of the elastic wave resonator 1 caused by temperature changes. Examples of materials for such a support substrate 3 include sapphire (Al2O3), silicon carbide (SiC), and silicon (Si).

[0033] The acoustic reflector layer 5 is located on the lower surface 2b side of the piezoelectric layer 2 (in direct or indirect contact), between the piezoelectric layer 2 and the support substrate 3. The acoustic impedance of the acoustic reflector layer 5 is different from that of the piezoelectric layer 2. In this case, an acoustic impedance difference is generated between the piezoelectric layer 2 and the acoustic reflector layer 5, thus effectively encapsulating the excited elastic wave within the piezoelectric layer 2.

[0034] The acoustic reflector layer 5 can be composed of a single layer or multiple layers. For example, the acoustic reflector layer 5 can also be composed of multiple low acoustic impedance layers 51 and multiple high acoustic impedance layers 52 stacked alternately. The acoustic impedance of the low acoustic impedance layer 51 is less than the acoustic impedance of the piezoelectric layer 2. The acoustic impedance of the high acoustic impedance layer 52 is greater than the acoustic impedance of the low acoustic impedance layer 51. With this structure, elastic waves leaking from the lower surface 2b side of the piezoelectric layer 2 are reflected towards the piezoelectric layer 2 side by the interface between the low acoustic impedance layer 51 and the high acoustic impedance layer 52, thus more effectively reducing the leakage of elastic waves.

[0035] Examples of materials that can be used as the low acoustic impedance layer 51 are silicon oxide (SiO2). Examples of materials that can be used as the high acoustic impedance layer 52 are hafnium oxide (HfO2), tantalum oxide (Ta2O5), tungsten (W), molybdenum (Mo), and zirconium oxide (ZrO2).

[0036] The IDT electrode 4 is located on the upper surface 2a side of the piezoelectric layer 2. The IDT electrode 4 is made of a conductive material. The material of the IDT electrode 4 can be various conductive materials such as aluminum (Al), copper (Cu), platinum (Pt), molybdenum (Mo), gold (Au), or alloys thereof. Alternatively, the IDT electrode 4 can be constructed by stacking multiple layers formed of the aforementioned conductive materials. Furthermore, when the IDT electrode 4 is constructed by stacking multiple layers, an anti-diffusion layer made of a metal such as titanium (Ti) or a dielectric can be interposed at the stacking interface. The layer of the IDT electrode 4 located on the piezoelectric layer 2 side can be a base layer made of a metal such as titanium (Ti) or a dielectric. In one embodiment of this disclosure, specifically, the IDT electrode 4 is Al.

[0037] Figure 2 This is a top view of an elastic wave resonator 1 according to an embodiment of this disclosure, viewed from the Z-axis direction. (See image below.) Figure 2 As shown, the IDT electrode 4 has a comb-shaped electrode 41. The comb-shaped electrode 41 includes a plurality of electrode fingers 412 arranged in a specific order. Additionally, the comb-shaped electrode 41 includes a pair of busbars 411 located in a direction intersecting the arrangement direction of the plurality of electrode fingers 412 and connected to the plurality of electrode fingers 412. In other words, the plurality of electrode fingers 412 extend from the busbars 411. The plurality of electrode fingers 412 are arranged in a manner that engages with each other, with a plurality of electrode fingers 412a connected to one busbar 411a and electrode fingers 412b connected to the other busbar 411b. Furthermore, in Figure 2 In one embodiment described herein, the arrangement direction of the plurality of electrode fingers 412 is the X-axis direction, and the extension direction of the plurality of electrode fingers 412 is the Y-axis direction.

[0038] The comb-shaped electrode 41 may also include a plurality of virtual electrode fingers 413 located between each of the plurality of electrode fingers 412. The plurality of virtual electrode fingers 413 have: a plurality of virtual electrode fingers 413a connected to one busbar 411a and facing an electrode finger 412b extending from another busbar 411b; and a plurality of virtual electrode fingers 413b connected to one busbar 411b and facing an electrode finger 412a extending from another busbar 411a. Furthermore, in this disclosure, "facing" does not necessarily require that the facing surfaces be parallel to each other; the facing surfaces may also be inclined.

[0039] The lengths of the extension directions of the plurality of electrode fingers 412 can be appropriately set according to the required electrical characteristics, etc. For example, the lengths of the extension directions of the plurality of electrode fingers 412 are equal to each other. In addition, the IDT electrode 4 can also be implemented to vary the lengths of the extension directions of the plurality of electrode fingers 412 according to the position in the X-axis direction, a process known as apodization.

[0040] The repeating interval in the arrangement direction of the plurality of electrode fingers 412 is defined as the spacing P. The spacing P is appropriately designed according to the desired frequency characteristics. Figure 2 In this example, the spacing P is constant, but not limited to this one. For example, the spacing P can be designed to gradually increase, or it can be designed to have multiple repetition intervals in stages. In the case of multiple different repetition intervals, the spacing P can also be defined based on the average value of the repetition intervals measured at 5 to 10 locations, or it can be defined by using the largest repetition interval as a representative. The specific value of the spacing P is arbitrary. For example, the spacing P can be 0.5 μm or more, or 1 μm or more, or it can be 10 μm or less, 5 μm or less, or 2 μm or less. The examples of the lower limit and the upper limit mentioned above can be combined arbitrarily. Furthermore, specifically, in one embodiment of this disclosure, the spacing P of the electrode fingers 412 is 1.1 μm.

[0041] When a high-frequency signal is applied to the IDT electrode 4, an elastic wave with a wavelength λ, defined as twice the repetition interval P of the plurality of electrode fingers 412, is excited and propagates in the piezoelectric layer 2. Furthermore, unlike the above, the wavelength λ can be less dependent on the spacing P, similar to a bulk wave propagating along the thickness direction of the piezoelectric layer 2. Additionally, λ can be defined as twice the spacing P for the thickness of the piezoelectric layer 2, etc., and can also deviate from the wavelength of the elastic wave excited as the main resonance.

[0042] In one embodiment of this disclosure, the elastic wave resonator 1 may also have (or may not have) a pair of reflectors 42 located on the upper surface 2a side of the piezoelectric layer 2. For example, the pair of reflectors 42 are located on both sides of the comb-shaped electrode 41 in the X-axis direction. The reflectors 42 include a pair of reflector busbars 421 facing each other and a plurality of strip electrodes 422 extending between the pair of reflector busbars 421.

[0043] Figure 3 A and Figure 3 Figure B is a schematic cross-sectional view of the elastic wave resonator 1 of one embodiment of this disclosure, viewed from the Y-axis direction, and is an enlarged view of the portion with electrode finger 412. In other words, Figure 3 A and Figure 3 B is a cross-sectional view viewed from the direction of extension of electrode finger 412.

[0044] In an embodiment of the elastic wave resonator 1 of this disclosure, the piezoelectric layer 2 has a groove 21 on its upper surface 2a. At least a portion of a plurality of electrode fingers 412 is located within the groove 21. All of the plurality of electrode fingers 412 may also be located within the groove 21, but this is not a limitation. For example, electrode fingers 412 located within the groove 21 and electrode fingers 412 located outside the groove 21 may coexist. Furthermore, the entire thickness (and / or volume) of the electrode fingers 412 located within the groove 21 may also be located within the groove 21. However, this is not a limitation. For example, at least a portion (e.g., the lower part) of the thickness (and / or volume) of the electrode fingers 412 may be located within the groove 21. Moreover, to distinguish it from the protruding region 46 described later, the region located within the groove 21 of the electrode fingers 412 is referred to as the embedded region 45.

[0045] like Figure 3 As shown in Figure A, the embedded region 45 within the groove 21 of the electrode finger 412 has a wide region 43 and a narrow region 44. The width of the electrode finger 412 in the narrow region 44 is narrower than the width of the electrode finger 412 in the wide region 43. In other words, when the width of the electrode finger 412 in the wide region 43 is set as T1 and the width of the electrode finger 412 in the narrow region 44 is set as T2, then T1 > T2. Furthermore, T1 can be the width of any part of the wide region 43, and T2 can also be the width of any part of the narrow region 44. For example, T1 can be the width of the widest part of the wide region 43, and T2 can be the width of the narrowest part of the narrow region 44. In addition, the "width" of the electrode finger 412 refers to the length of the electrode finger 412 in the X-axis direction.

[0046] Which portion of the electrode finger 412 is designated as the narrow region 44 and the wide region 43 can be determined by comparing the widths of the measured portions. The region narrower than the narrowest portion of the wide region 43 is designated as the narrow region 44, and the region wider than the widest portion of the narrow region 44 is designated as the wide region 43. In other words, the overall width of the wide region 43 is wider than the overall width of the narrow region 44, and the overall width of the narrow region 44 is narrower than the overall width of the wide region 43. Furthermore, the embedding region 45 of the electrode finger 412 can have a plurality of wide regions 43 or a plurality of narrow regions 44.

[0047] like Figure 3As shown in B, the specific cross-sectional shape of the electrode finger 412 in one embodiment of this disclosure, viewed from the extension direction, is a trapezoid with the main surface located on the opening side of the groove 21 as the upper base 451, the main surface located on the bottom side of the groove 21 as the lower base 452, and the side surface as the waist 453. Thus, when the cross-sectional shape viewed from the extension direction of the electrode finger 412 is trapezoidal, the narrow region 44 is located closer to the lower surface 2b of the piezoelectric layer 2 than the wide region 43.

[0048] As shown in one embodiment of this disclosure, when the embedding region 45 of the electrode fingers 412 has a structure with a wide region 43 and a narrow region 44, the spacing P1 of the electrode fingers 412 in the wide region 43 can be different from the spacing P2 of the electrode fingers 412 in the narrow region 44. Furthermore, the aforementioned spacing P is a parameter unaffected by the width of the electrode fingers 412, such as the center-to-center distance between adjacent electrode fingers 412. Spacings P1 and P2 are parameters affected by the width of the electrode fingers 412, such as the distance (interval) between the sides of adjacent electrode fingers 412.

[0049] Generally, when the spacing (e.g., P1 and P2) of the electrode fingers 412 differs in the thickness direction, the main mode, which is the primary resonance, and the clutter mode, which is an unwanted wave, are unlikely to resonate, and the phase intensity of both is reduced. However, in one embodiment of this disclosure, since at least one of the plate wave and the volume wave, which are less affected by the spacing difference, is used as the primary resonance, even if the spacing P1 of the electrode fingers 412 in the wide region 43 and the spacing P2 of the electrode fingers 412 in the narrow region 44 are different, the influence on the frequency characteristics of the primary resonance can be reduced. Therefore, according to one embodiment of this disclosure, the frequency characteristics of the primary resonance can be well maintained and clutter can be effectively reduced.

[0050] The effects based on the wide region 43 and the narrow region 44 can be qualitatively explained as described above. Therefore, the specific values ​​of the width and thickness of the electrode finger 412 and the width and thickness of the groove 21 are arbitrary. For example, T1 / P and / or T2 / P can be 0.05 or more, 0.2 or more, or 0.3 or more, or they can be 0.6 or less, 0.5 or less, or 0.3 or less. As long as the above lower and upper limits do not contradict each other, they can be combined arbitrarily. In addition, for example, on the premise that the thickness of the electrode finger 412 and / or the depth of the groove 21 is less than or equal to the thickness of the piezoelectric layer 2, they can be 0.005λ or more, 0.01λ or more, 0.02λ or more, or 0.04λ or more, or they can be 0.5λ or less, 0.3λ or less, or 0.1λ or less. The above lower and upper limits can also be combined arbitrarily. Furthermore, the thicker the electrode finger 412, the easier it is to realize the above-mentioned structure and effects of the electrode finger 412.

[0051] Figure 4The simulation results show the frequency characteristics of the elastic wave resonator 1 according to one embodiment of this disclosure. Solid lines represent... Figure 1 and Figure 3 The simulation results for Example 1 are shown below, with dashed lines representing the simulation results for comparative examples. In Example 1, as... Figure 3 As shown, the side of the electrode finger 412 is tilted, and the cross-sectional shape of the embedding area 45 of the electrode finger 412 is formed into a trapezoid. In the comparative example, the side of the electrode finger 412 is not tilted, and the cross-sectional shape of the embedding area 45 is formed into a rectangle.

[0052] Depend on Figure 4 As can be seen, compared with the comparative example, the embodiment reduces the clutter generated in the vicinity of 6000MHz to 6500MHz. On the other hand, it has little impact on the characteristics of the main resonance located in the vicinity of 5400MHz to 5800MHz. Thus, according to one embodiment of the present disclosure, an elastic wave resonator with excellent frequency characteristics can be provided.

[0053] The cross-sectional shape of the embedded region 45 of electrode 412, as well as the positional relationship between the wide region 43 and the narrow region 44, can be appropriately designed. Figure 5 A~ Figure 5 C shows another example of an elastic wave resonator 1 in this disclosure.

[0054] exist Figure 1 In one embodiment, the narrow region 44 is configured to be located closer to the lower surface 2b of the piezoelectric layer 2 than the wide region 43, but this is not a limitation of the example. For example, in Figure 5 In the example shown in A, the narrow region 44 is located closer to the upper surface 2a of the piezoelectric layer 2 than the wide region 43.

[0055] exist Figure 1 In one embodiment described, the cross-sectional shape of the embedding region 45 of the electrode finger 412 is a trapezoid with the main surface located on the bottom side of the groove 21 as the lower base and the side surface as the waist, but it is not limited to this example. For example, in Figure 5 In the example shown in B, the cross-sectional shape of the embedded region 45 of the electrode finger 412 is a combination of a wide rectangular region 43 and a narrow rectangular region 44. Furthermore, in Figure 5 In the example shown in B, the narrow region 44 is located closer to the lower surface 2b of the piezoelectric layer 2 than the wide region 43.

[0056] exist Figure 1 In one embodiment described, an example is shown where the entire electrode finger 412 is located within the groove 21, but this is not a limitation. For example, in Figure 5In the example shown in C, a portion of the electrode finger 412 may be located within the groove 21, and a portion may be located outside the groove 21. The area of ​​the electrode finger 412 located outside the groove 21 is designated as the protruding area 46. Furthermore, the width of the protruding area 46 can be appropriately set. For example, the width of the protruding area 46 may be greater than or less than the width of the narrow area 44 in the embedded area 45.

[0057] Furthermore, the length of the protruding region 46 in the Z-axis direction can be less than the length of the embedded region 45 in the Z-axis direction. In other words, the amount of protrusion in the protruding region 46 as observed from the piezoelectric layer 2 can be less than the amount of embedment in the embedded region 45. In this case, the effect of reducing clutter in the embedded region 45 is more effective.

[0058] In addition, Figure 1 In the elastic wave resonator 1 of one embodiment of the present disclosure described herein, the acoustic reflection layer 5 represents an example of a solid layer, but is not limited to this example. For example, as other embodiments of the present disclosure, such as Figure 6 As shown, a gap 53 may also be present between the piezoelectric layer 2 and the support substrate 3. A gas is present in the gap 53. Furthermore, the gas can be air, or an inactive gas such as nitrogen or argon. The support substrate 3 may also be in direct or indirect contact with the piezoelectric layer 2.

[0059] The gap 53 exists at the position where it overlaps with the plurality of electrode fingers 412 when viewed from a plane along the Z-axis. By adopting such a structure, the gas present in the gap 53 acts as an acoustic reflector layer, effectively reducing the leakage of elastic waves from the lower surface 2b side of the piezoelectric layer 2. Furthermore, the size and depth of the gap 53 can be appropriately set.

[0060] like Figure 3 As shown in B, when the cross-sectional shape of the electrode finger 412 in one embodiment of this disclosure is trapezoidal when viewed from its extension direction, the angle θ between the upper base 451 and the waist 453 can be any value within a range of less than 90°. The larger the angle θ, the greater the difference between the width of the electrode finger 412 in the wide region 43 and the width of the electrode finger 412 in the narrow region 44. As a result, the difference between the spacing P1 of the electrode fingers 412 in the wide region 43 and the spacing P2 of the electrode fingers 412 in the narrow region 44 also increases, thus enabling more effective reduction of clutter.

[0061] For example, the angle θ formed by the upper base 451 and the waist 453 can be greater than 35° and less than 90°. Figure 7 A and Figure 7 B is a graph representing the simulation results of the frequency characteristics when the angle θ is varied in Embodiments 1 and 2 of this disclosure. Figure 7 A and Figure 7 The vertical axis of B represents the bandwidth Δf (%) of the primary resonance, and the horizontal axis represents the angle θ (°). Furthermore, in this specification, when the resonant frequency of the elastic wave resonator 1 is set to fr and the anti-resonant frequency to fa, the bandwidth Δf is defined as (fa-fr)×100 / fr. The larger the bandwidth Δf of the primary resonance, the larger the bandwidth of the filter, thus improving the frequency response.

[0062] Figure 7 A is the simulation result of the frequency characteristics of Example 1. Figure 7 B is the simulation result of the frequency characteristics of Example 2. Example 1 is... Figure 1 In one embodiment described herein, an acoustic reflection layer 5, on the lower surface 2b side of the piezoelectric layer 2, is provided, in which a low acoustic impedance layer 51 and a high acoustic impedance layer 52 are stacked. Embodiment 2 is... Figure 6 In one embodiment described herein, a void 53 exists on the lower surface 2b side of the piezoelectric layer 2. Furthermore, the piezoelectric layer 2 in both Embodiment 1 and Embodiment 2 is LT. The detailed designs of Embodiment 1 and Embodiment 2 are shown below.

[0063] The conditions used in Examples 1 and 2 (piezoelectric layer: LT, piezoelectric layer Euler angle: (0°, 31°, 0°), piezoelectric layer thickness: 0.40 μm, IDT electrode: Al, spacing P: 1.1 μm, T1 / P: 0.5, electrode thickness: 0.13 μm, support substrate: Si)

[0064] Example 1 (Low acoustic impedance layer: SiO2, High acoustic impedance layer: HfO2)

[0065] Example 2 (with gaps)

[0066] By keeping the width T1 and electrode thickness constant and by varying the width T2, the angle θ is changed.

[0067] Depend on Figure 7 A and Figure 7 As shown in B, when the angle θ is greater than 35° and less than 90°, the specific bandwidth Δf increases compared to when the angle θ is 90°. Therefore, when the angle θ is greater than 35° and less than 90°, it can reduce clutter and increase the specific bandwidth Δf, thereby improving the characteristics of the main resonance.

[0068] Furthermore, the angle θ can be within a range greater than 35° and less than 85°. In this case, the specific bandwidth Δf can be increased more effectively. Additionally, the angle θ can be within a range greater than 35° and less than 80°. In this case, the specific bandwidth Δf can be increased more effectively. Furthermore, the angle θ can be within a range greater than 35° and less than 70°. In this case, the specific bandwidth Δf can be increased more effectively.

[0069] In addition, the angle θ formed by the upper base 451 and the waist 453 can also be within the range of greater than 45° and less than 90°. Figure 8 A and Figure 8 B is a graph representing the simulation results of the frequency characteristics when the angle θ is varied in Embodiments 1 and 2 of this disclosure. Figure 8 A and Figure 8 The vertical axis of B represents the peak value of the primary resonance, PV, and the horizontal axis represents the angle θ (°). Furthermore, in this specification, PV is defined as the value obtained by dividing the absolute value of the impedance at the anti-resonance frequency fa of the elastic wave resonator 1, |Z|, by the absolute value of the impedance at the resonance frequency fr, |Z|. In other words, PV = (|Z| in fa) / (|Z| in fr). A larger PV of the primary resonance results in better steepness and loss characteristics as a filter, thus improving frequency response.

[0070] Figure 8 A is the simulation result of the frequency characteristics of Example 1. Figure 8 B is the simulation result of the frequency characteristics of Example 2.

[0071] Depend on Figure 8 A and Figure 8 As shown in B, when the angle θ is in the range of greater than 45° and less than 90°, PV increases as it would when the angle θ is 90°. Therefore, when the angle θ is in the range of greater than 45° and less than 90°, clutter can be reduced and PV can be increased, thus improving the characteristics of the main resonance.

[0072] Furthermore, the angle θ can also be within the range of greater than 45° and less than 85°. In this case, PV can be increased more effectively. Additionally, the angle θ can also be within the range of greater than 45° and less than 80°. In this case, PV can be increased more effectively. Furthermore, the angle θ can also be within the range of greater than 45° and less than 70°. In this case, PV can be increased more effectively.

[0073] For example, the angle θ formed by the upper base 451 and the waist 453 can be greater than 55° and less than 90°. Figure 9 A and Figure 9 B is a graph representing the simulation results of the frequency characteristics when the angle θ is changed for Embodiments 3 and 4, which are embodiments of this disclosure. Figure 9 A and Figure 9 The vertical axis of B represents the frequency band ratio Δf (%) of the main resonance, and the horizontal axis represents the angle θ (°).

[0074] Figure 9 A represents the simulation result of the frequency characteristics of Example 3. Figure 9B is the simulation result of the frequency characteristics of Example 4. Example 3 is... Figure 1 In one embodiment described herein, an acoustic reflection layer 5, on the lower surface 2b side of the piezoelectric layer 2, has an overlapping low acoustic impedance layer 51 and a high acoustic impedance layer 52. Example 4 is... Figure 6 In one embodiment described herein, a void 53 exists on the lower surface 2b side of the piezoelectric layer 2. Furthermore, the piezoelectric layer 2 in both Embodiments 3 and 4 is LN. The detailed designs of Embodiments 3 and 4 are shown below.

[0075] The conditions used in Examples 3 and 4 (piezoelectric layer: LN, piezoelectric layer Euler angle: (0°, 35°, 0°), piezoelectric layer thickness: 0.37 μm, IDT electrode: Al, spacing P: 1.1 μm, T1 / P: 0.5, electrode thickness: 0.11 μm, support substrate: Si)

[0076] Example 3 (Low acoustic impedance layer: SiO2, High acoustic impedance layer: HfO2)

[0077] Example 4 (with gaps)

[0078] By keeping the width T1 and electrode thickness constant and varying the width T2, the angle θ can be changed.

[0079] Depend on Figure 9 A and Figure 9 As shown in B, when the angle θ is in the range of greater than 55° and less than 90°, the specific bandwidth Δf becomes larger (or becomes equal) compared to when the angle θ is 90°. Therefore, when the angle θ is in the range of greater than 55° and less than 90°, it is possible to reduce clutter and increase the specific bandwidth Δf, thereby improving the characteristics of the main resonance.

[0080] Furthermore, the angle θ can also be in the range of greater than 55° and less than 85°. In this case, the specific bandwidth Δf can be increased more effectively. Additionally, the angle θ can also be in the range of greater than 55° and less than 80°. In this case, the specific bandwidth Δf can be increased more effectively. Furthermore, the angle θ can also be in the range of greater than 55° and less than 70°. In this case, the specific bandwidth Δf can be increased more effectively.

[0081] In addition, the angle θ formed by the upper base 451 and the waist 453 can be greater than 45° and less than 90°. Figure 10 A and Figure 10 B is a graph representing the simulation results of the frequency characteristics when the angle θ is changed for Embodiments 3 and 4, which are embodiments of this disclosure. Figure 10 A and Figure 10 The vertical axis of B represents the PV value of the principal resonance, and the horizontal axis represents the angle θ (°).

[0082] Figure 10 A represents the simulation result of the frequency characteristics of Example 3. Figure 10 B is the simulation result of the frequency characteristics of Example 4.

[0083] Depend on Figure 10 A and Figure 10 As shown in B, when the angle θ is in the range of greater than 45° and less than 90°, PV increases as it would when the angle θ is 90°. Therefore, when the angle θ is in the range of greater than 45° and less than 90°, clutter can be reduced and PV can be increased, thus improving the characteristics of the main resonance.

[0084] Furthermore, the angle θ can also be within the range of greater than 45° and less than 85°. In this case, PV can be increased more effectively. Additionally, the angle θ can also be within the range of greater than 45° and less than 80°. In this case, PV can be increased more effectively. Furthermore, the angle θ can also be within the range of greater than 45° and less than 70°. In this case, PV can be increased more effectively.

[0085] Although no specific illustration is provided, the applicant has confirmed that, under the conditions of Examples 1 to 4, even when the spacing P is set to 5 μm and T1 / P is set to 0.06, clutter reduction can be achieved through simulation calculations.

[0086] Furthermore, a "trapezoid" does not necessarily have to be a strict trapezoid. For example, the angles of a trapezoid can be rounded. Additionally, the upper base, lower base, and legs do not necessarily have to be strictly straight lines. For example, the upper base, lower base, and legs can also be formed as rounded curves. Moreover, in this case, the angle θ between the upper base and the legs can be calculated, for example, as the angle between the tangent at the midpoint of the upper base and the tangent at the midpoint of the legs.

[0087] Alternatively, a portion of the trapezoid may have a concave or convex part. In this case, the angle θ between the upper base and the waist can be determined, for example, as the angle between a line that roughly overlaps with the portion of the upper base except for the concave or convex part and a line that roughly overlaps with the portion of the waist except for the concave or convex part.

[0088] The cross-sectional shape of the electrode finger 412 can be achieved using various methods. For example, a groove 21 is formed on the piezoelectric layer 2, and the cross-sectional shape of the groove 21 is formed into a desired shape such as a trapezoid. Then, a metal layer is formed to become the electrode finger 412. At this time, by filling the groove 21 with the metal layer, the cross-sectional shape of the electrode finger 412 becomes the same as the cross-sectional shape of the groove 21, and thus becomes a desired shape such as a trapezoid. The method of forming the groove 21 with the desired cross-sectional shape can be various. For example, the groove 21 can also be formed by etching (e.g., wet etching). Moreover, the cross-sectional shape such as a trapezoid can be achieved by using the anisotropy of single-crystal etching or by sequentially performing etching under different conditions. In addition, the groove 21 can also be formed by laser processing, for example. Moreover, the cross-sectional shape such as a trapezoid can be achieved by using the conical or inverted conical shape of the laser or by sequentially performing etching under different conditions.

[0089] (Example of the use of elastic wave resonator 1: wave demultiplexer)

[0090] Figure 11 This is a circuit diagram schematically illustrating the structure of a demultiplexer 101 as an example of the use of the elastic wave resonator 1. As can be understood from the reference numerals shown in the upper left of the page of this figure, in... Figure 11 In the diagram, the comb-shaped electrode 41 is schematically represented by the shape of a fork, and the reflector 42 is represented by a line with both ends bent.

[0091] The demultiplexer 101 includes, for example, a transmit filter 105 that filters the transmit signal from the transmit terminal 103 and outputs it to the antenna terminal 102; and a receive filter 106 that filters the receive signal from the antenna terminal 102 and outputs it to the receive terminal 104.

[0092] Furthermore, the transmit filter 105 and the receive filter 106 are, for example, rudder-type filters, which are constructed by connecting a plurality of resonators in a rudder-like configuration. That is, the transmit filter 105 has: one or more series resonators connected in series between the transmit terminal 103 and the antenna terminal 102; and one or more parallel resonators connecting the series arm and the reference potential.

[0093] For example, the elastic wave resonator 1 in one embodiment of this disclosure may also be used as at least one of the series resonators or parallel resonators of the transmitting filter 105 and the receiving filter 106.

[0094] Figure 11 This is just one example of the structure of the demultiplexer 101; the demultiplexer 101 is not limited to... Figure 11 The structure. For example, the transmit filter 105 can be composed of a multimode filter, etc. Additionally, in Figure 11In this design, both the transmitting filter 105 and the receiving filter 106 are elastic wave filters, but the design is not limited to this structure. For example, one of the transmitting filter 105 and the receiving filter 106 may be an elastic wave filter using an elastic wave resonator 1, and the other may be an LC filter including one or more inductors and one or more capacitors.

[0095] Furthermore, although the case where the demultiplexer 101 has a transmit filter 105 and a receive filter 106 has been described, the demultiplexer 101 is not limited to this structure. For example, the demultiplexer 101 can be a duplexer or a multiplexer that includes three or more filters.

[0096] (Example of application of elastic wave resonator 1: communication device)

[0097] Figure 12 This is a block diagram showing the main parts of a communication device 111, which is an example of the use of an elastic wave resonator 1 and a demultiplexer 101. The communication device 111 includes a demultiplexer 101 for wireless communication utilizing radio waves.

[0098] In the communication device 111, the transmission information signal TIS, which includes the information to be transmitted, is modulated and frequency-boosted by the RF-IC (Radio Frequency Integrated Circuit) 113 to become the transmission signal TS. The transmission signal TS is filtered by a bandpass filter 115a to remove unwanted components outside the transmission passband, amplified by an amplifier 114a, and then input to the transmission terminal 103. Then, the transmission filter 105 removes unwanted components outside the transmission passband from the input transmission signal TS, and outputs the removed transmission signal TS from the antenna terminal 102 to the antenna 112. The antenna 112 converts the input transmission signal TS into a wireless signal and transmits it.

[0099] In addition, in the communication device 111, the wireless signal received by the antenna 112 is converted into a received signal RS by the antenna 112 and input to the antenna terminal 102. The receive filter 106 removes unwanted components outside the receive passband from the input received signal RS and outputs it from the receive terminal 104 to the amplifier 114b. The output received signal RS is amplified by the amplifier 114b and unwanted components outside the receive passband are removed by the bandpass filter 115b. Then, the received signal RS is frequency-reduced and demodulated by the RF-IC 113 to become the received information signal RIS.

[0100] Furthermore, the Transmit Information Signal (TIS) and Receive Information Signal (RIS) can be low-frequency signals containing appropriate information, such as analog or digitized audio signals. The passband of the wireless signal can be appropriately set, and in one embodiment of this disclosure, it can also be a relatively high-frequency passband. The modulation method can be phase modulation, amplitude modulation, frequency modulation, or any combination of two or more of these. Figure 12 The example provided illustrates a direct conversion circuit, but it is not limited to this example; for instance, a double superheterodyne circuit could also be used. Additionally, Figure 12 The main parts are shown only schematically. Low-pass filters or isolators can be added in appropriate places, and the positions of amplifiers can also be changed.

[0101] Explanation of reference numerals in the attached figures

[0102] 1: Elastic wave resonator

[0103] 2: Piezoelectric layer

[0104] 2a: Top surface (first surface)

[0105] 2b: Lower surface (second surface)

[0106] 21: Slot

[0107] 3: Supporting substrate

[0108] 4: IDT electrode

[0109] 41: Comb-shaped electrode

[0110] 411: Busbar

[0111] 412: Electrode finger (first electrode finger)

[0112] 42: Reflector

[0113] 43: Wide area

[0114] 44: Narrow area

[0115] 45: Burial Area

[0116] 46: Protruding area

[0117] 451: Upper bottom

[0118] 452: Bottom

[0119] 453: waist

[0120] 5: Acoustic reflector layer

[0121] 51: Low acoustic impedance layer

[0122] 52: High Acoustic Impedance Layer

[0123] 53: Gap

[0124] 101: Demultiplexer

[0125] 102: Antenna terminal

[0126] 103: Transmitter Terminal

[0127] 104: Receiver terminal

[0128] 111: Communication device

[0129] 112: Antenna

[0130] 113: RF-IC

[0131] 114: Amplifier

[0132] 115: Bandpass filter

Claims

1. An elastic wave resonator, wherein, have: The piezoelectric layer has a groove on its first surface and exhibits piezoelectricity; and A plurality of electrode fingers, including at least a portion of a first electrode finger located within the groove; In a cross-sectional view taken from the extension direction of the plurality of electrode fingers, the region of the first electrode finger located within the groove has a wide region and a narrow region that is narrower than the wide region. At least one of the excitation plate wave and the body wave serves as the primary resonance.

2. The elastic wave resonator according to claim 1, wherein, The piezoelectric layer has a second surface located opposite to the first surface; The narrow region is located closer to the second surface than the wide region.

3. The elastic wave resonator according to claim 1 or 2, wherein, In the cross-sectional view, the first electrode refers to a trapezoid with the surface located on the opening side of the groove as the upper base, the surface located on the bottom side of the groove as the lower base, and the side surface as the waist.

4. The elastic wave resonator according to claim 3, wherein, In the cross-sectional view, the angle between the upper base and the waist is greater than 35° and less than 90°.

5. The elastic wave resonator according to claim 3, wherein, In the cross-sectional view, the angle between the upper base and the waist is greater than 45° and less than 90°.

6. The elastic wave resonator according to claim 3, wherein, In the cross-sectional view, the angle between the upper base and the waist is greater than 55° and less than 90°.

7. The elastic wave resonator according to any one of claims 1 to 6, wherein, The A1 mode Lamb wave is used as the main resonance.

8. The elastic wave resonator according to any one of claims 1 to 7, wherein, The thickness of the piezoelectric layer is less than twice the repeating interval of the plurality of electrode fingers.

9. The elastic wave resonator according to any one of claims 1 to 8, wherein, The piezoelectric layer contains lithium tantalate or lithium niobate.

10. The elastic wave resonator according to any one of claims 1 to 9, wherein, It also has an acoustic reflective layer that is in direct or indirect contact with the piezoelectric layer; The acoustic reflector layer is composed of alternating layers of a plurality of low acoustic impedance layers with an acoustic impedance lower than that of the piezoelectric layer and a plurality of high acoustic impedance layers with an acoustic impedance higher than that of the plurality of low acoustic impedance layers.

11. The elastic wave resonator according to any one of claims 1 to 10, wherein, It also has a supporting substrate that is in direct or indirect contact with the piezoelectric layer; It has a gap located between the piezoelectric layer and the supporting substrate; The gap overlaps with a plurality of the electrode fingers in a planar perspective view taken from a direction orthogonal to the first surface.

12. A communication device, wherein, have: antenna; An elastic wave filter connected to the antenna; and IC connected to the elastic wave filter; The elastic wave filter includes the elastic wave resonator according to any one of claims 1 to 11.

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